Noncohering thin sheeting



Oct. 12, 1943.

cs. F. NADEAU EI'AL I 2,331,715 NONCOHERING THIN SHEE'I'ING Filed July 20, 1940 FIG. I. I 4

PHOTOMICROGRAPH OF SURFACE OF SHEET BEARING ADHERENT DEPOSIT OF FINE DISCRETE PARTICLES OF PROLAMINE GALE F. NADEAU EDWIN H. HILBORN INVENTORS fiwzw I A ORNEYS Patented Oct. 12, 1943 NoNcoimmNG 'rmN YSHEETING at F. Nadeau and Edwin H. Hilborn, Bochester, N. I, assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application July 20, 1940, semi No. 346,546

9 Claims.

This invention dealswi-th thin, transparent, cellulose organic ester sheeting, such as is used in wrappin Packaging, etc. When such sheeting is cut into sheets, and a large number of the sheets are stacked together, ready for use in wrapping or in automatic packaging machinery, they cohere together, making it -difiicult to remove a sheet quickly from the pile without wrinkling. This is due to the absence of air between the perfectly smooth surfaces of the sheets. The dimculty is augmented by the strong tendency of cellulose organic esters, such as cellulose acetate, cellulose. acetate-propionate, cellulose acetate-butyrate, etc., to accumulate charges of static electricity. The tendency to accumulate static and to cohere is many times stronger-in cellulose organic ester sheets than in sheets of regenerated cellulose.

One object of .our invention is to. provide thin,

transparent cellulose organic ester sheeting of thewrapping type which will not cohere when stacked. Another object is to provide thin, transparent sheeting which will run smoothly through automatic packaging machinery. Other objects will hereinafter appear.

We have discovered that thin, transparent, cellulose organic ester sheeting which will fulfill the objects of our invention may be prepared by applying to the surface, of the sheeting an aqueous suspension of zein or other prolamine particles, and drying.

In carrying out our invention, we first prepare a solution of zein or other prolamine in a known solvent, such, for instance, as an aqueous alcohol,

preferably but not necessarily containing a wetting agent. A suspension is then formed by introducing the prolamine solution into a relatively large quantity of water containing an alkaline substance (preferably ammonia) and a wetting,

agent. The resulting aqueous suspension of prolamine particles may be applied to the cellulose organic ester sheeting at any timeafter the latter has set after casting; we prefer to apply it after the sheeting has been stripped from the casting surface, and before it has reached the wind-up.

Cellulose organic ester sheeting treated according to our invention is transparent-and entirely satisfactory for wrapping purposes, although a very slight haze may be seen when a pile of sheets is viewed. Individual sheets of it can be easily separated from a pile of the sheets in any kind We give, below, an example of the carrying out w of our inventio 4.5 lbs. of zein is stirred with a mixture of 56.25

lbs. of isopropyl alcohol, 2.25 lbs. of sodium dioctyl sulfo succinate (known as Aerosol OT) and 2'7 lbs. of water, until completely dissolved. The

solution is then stirred into 1000 lbs. of water containing 3 lbs. of 21.40% paste of sodium oleyl tauride (known as Arctic Syntex T) and 500 cc.

of 28% ammonia. The resulting suspension is diluted with 2000 lbs. of water, and is then ready for use. Thus, the finished suspension contains about 0.15% zein. The amount of zein may be varied over a rather wide range; from about 0.03% to about 1.00% being effective without causing objectionable haze in the sheeting.

In place of isopropyl alcohol, any of the lower aliphatic alcohols or alkoxy-alcohols which are of weather; it does not accumulate static to an I objectionable extent; it .is unusually flat; and it is not rendered tacky by-high humidity. It runs easily through automaticpackaging machinery.

miscible with water may be used, such, for in stance, as methyl alcohol; ethyl alcohol, propyl alcohol, butyl alcohol, the mono-ethyl ether of ethylene glycol, or the mono-methyl ether of ethylene glycol, Acetonemayalso be used in place of isopropyl alcohol. The ratio of organic solvent to water in the varied as desired, for instance from to alcohol, as long as the mixture is a solvent for zein.

While we prefer to use sodium dioctyl sulfo succinate in preparing the original zein solution,

because it may be obtained in a pure condition, is convenient to handle, and is soluble water mixtures, we may use other wetting agents, such, for instance, as sodium di-amyl sulfo succinate (Aerosol AY), sodium tri-isopropyl naphthalene sulfonate, sodium salts of alkylated phenols (such as Santomerse and Nacconal NR), etc. The amount of wetting agent in the original solution is not'important: the wetting agent may even be entirely dispensed with; However, we prefer to use an amount of wetting agent varying from 0.03% to 0.20% (calculated on the final suspension) in this solution, to insure uniform stability in the suspension prepared from the solu-,

tion. No harm would result from exceeding these proportions, but it would not be economical to do so.

We prefer to use ammonia as the alkaline substance in the suspension, because it can be evaporated from the sheeting during curing. However,. alkali metal hydroxides or carbonates may be substituted. The amount may be varied from about half that given in the above example to about four or five times that given in the example. Excessive amounts of strong alkali, howoriginal solution may be in alcoholever, would probably be detrimental to the sheetsuspension, we prefer to use sodium oleyl tauride as the wetting agent because it may be obtained in a pure form, free from salts, etc. However, many other wetting agents soluble in water may be substituted, such, for example, as salts of sulfated or sulfonatedaliphatic alcohols, salts of esters of sulfo succinic acid, salts of alkyl naphthalene sulfonic acid salts of sulfonated alkyl phenols, saponin, salts of 'sulfonated castor oil, etc. Here, again, the exact amount used is not important, Larger quantities than that shown in the example give no observable increase in efiiciency. It is believed that the, wetting agent assists in spreading the suspension of prolamine particles on the sheeting.

In place of zein, we may use any of the other prolamines, such as gliadin, hordein, or kafirin.

While we may apply the prolamine suspension to the sheeting before the latter has left the casting. surface, by means of a bead roll as shown in s U. S. Patent 2,036,377 of J. B. Wells, we prefer to apply it after the sheeting has left the casting surface, in order that water vapor will not be mixed with the cellulose ester solvent in the solvent recovery system. A convenient method of applying the prolamine suspension to the sheeting is diagrammatically shown in Fig. 1 of the accompanying drawing, forming a part hereof.

. In Fig. 1, 2 represents a coating roll or casting wheel of known character, such as is used in the manufacture of photographic film, on which the cellulose organic ester solution is spread by means of a hopper I adjusted to deliver the required amount of solution, and dried to form a thin sheet. The thin sheeting is stripped from the roll shortly before the wheel has made a complete revolution, passes over a guide-roll 3,

through a dryer 4, over a guide-roll 5, and under the guide roll I submerged in the prolamine suspension in an immersion pan 6 to such an extent that both sides of the sheeting are wet by the suspension. The suspension is kept at a temperature of 40 F. or lower. Any excess is removed from the sheeting by passing the sheeting between two idler rolls 8, one of which is of rubber and the other of steel, both in contact with the sheeting. The sheeting then passes over a guide roll 9, through a heated dryer l0-- to re- Inove water and solvent, and finally to a wind-up The suspension may be applied to the sheeting by spraying instead of by immersion. Many other variations may be made in the method of applying the prolamine suspension to the sheeting, without departing from our invention. For instance, the prolamine suspension may be applied to only one side of the sheeting.

Microscopic examination of sheeting treated by our novel process shows it to have on its surface enormous numbers of discrete particles of prolamine, rather uniformly distributed. Although no plastic binder for the particles is present, they show no perceptible tendency to dust off in handling. The average particle diameter of the dried zein particles on a piece of sheeting treated as described in the above example appears to be of the order of magnitude of IX 10* inch. Particles having an average diameter of from about 1 x 10 inch to about 1x10 inch appear to be most suitable for our invention.

Fig. 2 is a representation of a photomicrograph, magnification X-2685, of the surface of sheeting prepared according to our invention.

The particle size of the prolamine particles in the aqueous suspension, and hence of the dried particles on the sheeting, can be controlled in a number of ways. Rapid precipitation of the prolamine solution into a large amount of water gives smaller particles than precipitation into a small amount of water, followed by dilution with e. g., 0.003 inch in thickness, which is also useful for some wrapping purposes.

While we have spoken of cellulose organic ester sheeting, our invention is applicable to all thin sheeting made of organophile plastics, such, for example, as synthetic resins, the organophile cellulose ethers, etc.

What we claim as our invention and desire to be secured by Letters Patent of the United States is:

1. Thin, transparent, cellulose organic acid ester sheeting having on at least one surface an adherent deposit of fine, discrete particles of prolamine, free from plastic binder, whereby cohesion and static accumulation by the sheeting are prevented. i

2. Thin, transparent, cellulose organic acid ester sheeting having on at least one surface an adherent deposit of fine, discrete particles of zein, free from plastic binder, whereby cohesion and static accumulation by the sheeting are prevented.

3. Thin, transparent, cellulose organic acid ester sheeting having on at least one surface an adherent deposit of discrete zein particles having an average particle diameter of from 1 10 inch to 1x10 inch, free from plastic binder, whereby cohesion and static accumulation by the sheeting are prevented. v

4. A process of rendering thin, transparent, cellulose organic acid ester sheeting non-coherent and anti-static without objectionably impairing its transparency, comprising preparing a suspension of finely-divided prolamine particles by precipitating a prolamine solution into water containing an alkaline substance and a wetting agent, applying the prolamine suspension to at least one side of the cellulose organic ester sheeting, and drying the treated sheeting.

5. A process of rendering thin, transparent, cellulose organic acid ester sheeting non-coherent and anti-static without objectionably impairing its transparency, comprising preparing a suspension of finely-divided zein particles by precipitating a zein solution into-water containing an alkaline substance and a Wetting agent, applying water containing an alkaline substance and a wetting agent, applying the zein suspension to at least one side of the cellulose-organic ester sheeting, and drying the'treated sheeting.

7. Thin, transparent, organophile plastic sheeting a prolamine solution into water containing a wetting agent, applying the prolamine suspension to at least one'side of the organophile plastic sheeting, and drying the treated sheeting. V

9. A process of rendering thin, transparent, cellulose organic acid ester sheeting non-coherent and anti-static without objectionably impairing its transparency, comprising preparing a suspenF sion of finely-divided prolamine particles by precipitating a prolamine solution into water containing a wetting agent, applying the prolamine suspension to at least one side of the cellulose organic ester sheeting, and drying the treated sheeting. GALE F. NADEAU.

EDWIN H. I'll-BORN. 

